Method for the production of low-emission polyurethane soft foams

ABSTRACT

The present invention provides a process for producing low-emission flexible polyurethane foams having a reduced odor and reduced fogging by reacting a) polyisocyanates with b) compounds having at least two hydrogen atoms which are reactive toward isocyanate groups, c) blowing agents wherein polyether alcohols which have been prepared by addition of alkylene oxides onto compounds derived from renewable raw materials using DMC catalysts are used as compounds b) having at least two hydrogen atoms which are reactive toward isocyanate groups.

The present invention relates to a process for producing flexiblepolyurethane foams using polyether alcohols based on renewable rawmaterials, in particular castor oil.

Flexible polyurethane foams are used in many industrial fields, inparticular for upholestery or acoustic insulation. They are usuallyproduced by reacting polyisocyanates with compounds having at least twohydrogen atoms which are reactive toward isocyanate groups in thepresence of blowing agents and, if desired, catalysts and customaryauxiliaries and/or additives.

For ecological reasons, there is an increasing market demand for foamsbased on renewable raw materials. Such foams are usually produced usingpolyetherols which are prepared by addition of alkylene oxides ontocompounds derived from renewable raw materials.

Examples of compounds derived from renewable raw materials are castoroil, polyhydroxy fatty acids, ricinoleic acid, oils modified withhydroxyl groups, e.g. grapeseed oil, black caraway oil, pumpkin kerneloil, borage seed oil, soybean oil, wood germ oil, rapeseed oil,sunflower oil, peanut oil, apricot kernel oil, pistachio oil, almondoil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil,sesame oil, hemp oil, hazelnut oil, evening primrose oil, wild rose oil,thistle oil, walnut oil, fatty acids and fatty acid esters modified withhydroxyl groups and based on myristoleic acid, palmitoleic acid, oleicacid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid,nervonic acid, linoleic acid, α- and γ-linolenic acid, stearidonic acid,arachidonic acid, timnodonic acid, clupanodonic acid, cervonic acid.Among these, castor oil has the greatest industrial importance.

The reaction of the compounds derived from renewable raw materials withthe alkylene oxides can be carried out in a customary and known way. Itis usual to mix the starting compound with a catalyst and to react thismixture with alkylene oxides. The addition reaction with the alkyleneoxides usually occurs under the customary conditions, viz. at from 60 to180° C., preferably from 90 to 140° C., in particular from 100 to 130°C., and pressures in the range from 0 to 20 bar, preferably in the rangefrom 0 to 10 bar and in particular in the range from 0 to 5 bar.

As alkylene oxides, preference is given to using ethylene oxide,propylene oxide or any mixtures of these compounds.

As catalysts, preference is given to using basic compounds, among whichpotassium hydroxide has achieved the greatest industrial importance.

It is known from WO 00/44813 that multimetal cyanide compounds,frequently also referred to as DMC catalysts, can be used for thealkoxylation of castor oil.

The polyetherols for use in flexible foams preferably have a hydroxylnumber of from 20 to 100 mg KOH/g at a viscosity in the range from 400to 6000 mPa·s.

Flexible polyurethane foams produced from polyether alcohols which havebeen prepared on the basis of renewable raw materials such as castor oilusing basic catalysts display very poor properties in respect of odor,emissions and fogging.

Thus, the preparation of castor oil polyetherols results in theformation of considerable amounts of the ring of ricinoleic acid((R)-cis-12-hydroxy-9-octadecenoic acid).

This ring can be removed only incompletely by simple steam stripping.The polyether alcohols and the foams produced therefore displayemissions, odor and fogging. For this reason, use of these polyetherolsfor the production of flexible foams for furniture and mattresses orflexible foam for automobile applications is not acceptable on themarket. As an established commercial test method, the DaimlerChryslertest method PB VWL 709: “Analyse der flüchtigen Emissionen flüchtigerund kondensierbarer Substanzen aus Fahrzeuginnenraum Materialien mittelsThermodesorption” has become widely accepted.

The value for the emissions of volatile compounds will hereinafter bereferred to as the VOC value (VOC=volatile organic compounds). The valuefor the emissions of condensible compounds will hereinafter be referredto as the FOG value. In the test method, a target VOC value of 100 ppmand a target FOG value of 250 ppm are specified for flexible foams.These requirements set down by the automobile industry are increasinglyalso required by the foam processing industry and foam manufacturers.Polyetherols based on renewable raw materials, in particular castor oil,and prepared by means of basic catalysis, for example by means ofpotassium hydroxide catalysis, display VOC and FOG values onthermodesorption which are above the specific target values. The cyclicfatty acid esters contribute substantially to the high VOC and FOGvalues.

Further disadvantages are that flexible polyurethane foams produced frompolyether alcohols derived from renewable raw materials frequentlydisplay cracks or only an insufficient proportion of open cells. Theopportunities for making changes to the formulation, frequently referredto as processing range, is restricted when using such compounds.

A further disadvantage is that flexible polyurethane foams prepared frompolyether alcohols derived from renewable raw materials display a poorcompressive set. For example, the compressive set of flexible slabstockfoams determined in accordance with DIN EN 3386 is above 7% and afteraging in accordance with DIN EN ISO 2440 is above 10%.

It has surprisingly been found that the abovementioned disadvantages didnot occur when using polyether alcohols which had been prepared byaddition of alkylene oxides onto compounds derived from renewable rawmaterials using DMC catalysts. It was not necessary to subject thepolyether alcohols to steam stripping after their preparation.

The present invention accordingly provides a process for producinglow-emission flexible polyurethane foams having reduced odor and reducedfogging by reacting

-   a) polyisocyanates with-   b) compounds having at least two hydrogen atoms which are reactive    toward isocyanate groups,-   c) blowing agents    wherein polyether alcohols which have been prepared by addition of    alkylene oxides onto compounds derived from renewable raw materials    using DMC catalysts are used as compounds b) having at least two    hydrogen atoms which are reactive toward isocyanate groups.

The invention also provides the low-emission foams produced by theprocess of the present invention. These preferably have a maximum VOCvalue of 100 ppm, preferably 50 ppm and very preferably less than 20ppm, and a maximum FOG value of 200 ppm, preferably 100 ppm and verypreferably less than 50 ppm, in each case due to the constituents of thepolyol used according to the present invention in the polyurethane. Thevalues mentioned are determined in accordance with the DaimlerChryslertest method PB VWL 709: “Analyse der flüchtigen Emissionen flüchtigerund kondensierbarer Substanzen aus Fahrzeuginnenraum Materialien mittelsThermodesorption”. Furthermore, the foams produced by the process of thepresent invention have maximum odor values of the polyetherol usedaccording to the present invention of less than or equal to 2.0,preferably less than or equal to 1.7. The test method for the odor valueis given below.

The invention further provides for the use of polyether alcohols whichhave been prepared by addition of alkylene oxides onto compounds derivedfrom renewable raw materials using DMC catalysts for the production offlexible polyurethane foams having reduced odor and emissions, with themaximum odor value of the polyetherol used according to the presentinvention preferably being less than or equal to 2.0, particularlypreferably less than or equal to 1.7, and the flexible polyurethanefoams produced from the polyetherol used according to the presentinvention having a maximum VOC value of 100 ppm, preferably 50 ppm andvery preferably less than 20 ppm, due to the constituents of thepolyetherol used according to the present invention in the polyurethaneand a maximum FOG value of 200 ppm, preferably 100 ppm and verypreferably less than 50 ppm, due to the constituents of the polyol usedaccording to the present invention in the polyurethane. The valuesmentioned are determined by the DaimlerChrysler test method PB VWL 709:“Analyse der flüchtigen Emissionen flüchtiger und kondensierbarerSubstanzen aus Fahrzeuginnenraum Materialien mittels Thermodesorption”.

The invention further provides for the use of polyether alcohols whichhave been prepared by addition of alkylene oxides onto compounds derivedfrom renewable raw materials using DMC catalysts for the production offlexible polyurethane foams having reduced crack formation.

The invention further provides for the use of polyether alcohols whichhave been prepared by addition of alkylene oxides onto compounds derivedfrom renewable raw materials using DMC catalysts for the production offlexible polyurethane foams having reduced compressive sets.

The invention further provides for the use of polyether alcohols whichhave been prepared by addition of alkylene oxides onto compounds derivedfrom renewable raw materials using DMC catalysts for producing flexiblepolyurethane foams for use in motor vehicle interiors.

The invention further provides for the use of polyether alcohols whichhave been prepared by addition of alkylene oxides onto compounds derivedfrom renewable raw materials using DMC catalysts for producing flexiblepolyurethane foams for use in the production of furniture andmattresses.

As compounds derived from renewable raw materials, use is made of, inparticular, the above-described renewable or modified renewable rawmaterials such as oils, fatty acids and fatty acid esters which have amean OH functionality of at least 2-16, preferably from 2 to 8 and verypreferably from 2 to 4.

The polyether alcohols which are used according to the present inventionand have been prepared by addition of alkylene oxides onto compoundsderived from renewable raw materials using DMC catalysts preferably havea mean molecular weight in the range from 400 to 20000 g/mol, morepreferably from 1000 to 8000 g/mol.

The products from the addition of alkylene oxides onto compounds derivedfrom renewable raw materials using DMC catalysts preferably have acontent of cyclic fatty acid esters of not more than 50 ppm, morepreferably not more than 10 ppm.

The compounds derived from renewable raw materials are preferablyselected from the group consisting of castor oil, polyhydroxy fattyacids, ricinoleic acid, oils modified with hydroxyl groups, e.g.grapeseed oil, black caraway oil, pumpkin kernel oil, borage seed oil,soybean oil, wood germ oil, rapeseed oil, sunflower oil, peanut oil,apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia nutoil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil,evening primrose oil, wild rose oil, thistle oil, walnut oil, fattyacids and fatty acid esters modified with hydroxyl groups and based onmyristoleic acid, palmitoleic acid, oleic acid, vaccenic acid,petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleicacid, α- and γ-linolenic acid, stearidonic acid, arachidonic acid,timnodonic acid, clupanodonic acid, cervonic acid.

Examples of commercially available compounds which have been chemicallymodified by means of hydroxyl groups are Merginat® PV 204, 206 and 235,or the polyhydroxy fatty acid PHF 110 from Harburger Fettchemie.

Preference is given to using castor oil as compound derived fromrenewable raw materials.

According to the invention, polyether alcohols are prepared, asindicated, by addition of alkylene oxides onto H-functional startersubstances in the presence of DMC catalysts.

The DMC catalysts are generally known and are described, for example, inEP 654 302, EP 862 947, WO 99/16775, WO 00/74845, WO 00/74843 and WO00/74844.

As alkylene oxides, it is possible to use all known alkylene oxides, forexample ethylene oxide, propylene oxide, butylene oxide, styrene oxide.Particular preference is given to using ethylene oxide, propylene oxideand mixtures of the compounds mentioned as alkylene oxides.

The starter substances used are the abovementioned H-functionalcompounds derived from renewable raw materials.

The addition reaction of the alkylene oxides in the preparation of thepolyether alcohols used for the process of the present invention can becarried out by known methods. Thus, it is possible to use only onealkylene oxide for the preparation of the polyether alcohols. When aplurality of alkylene oxides are used, they can be added on in blocks,in which case the alkylene oxides are introduced individually insuccession, or can be added on randomly, in which case the alkyleneoxides are introduced simultaneously. It is also possible for bothblocks and random sections to be incorporated in the polyether chain inthe preparation of the polyether alcohols.

For the production of flexible polyurethane slabstock foams, preferenceis given to using polyether alcohols having a high content of secondaryhydroxyl groups and a content of ethylene oxide units in the polyetherchain of not more than 30% by weight, based on the weight of thepolyether alcohols. These polyether alcohols preferably have a propyleneoxide block at the end of the chain. Polyether alcohols used for theproduction of flexible polyurethane molded foams are, in particular,those having a high content of primary hydroxyl groups and an ethyleneoxide end block in an amount of <10% by weight, based on the weight ofthe polyether alcohol.

In a preferred embodiment of the addition reaction of mixtures of atleast two alkylene oxides, the ratio of the alkylene oxides to oneanother can be altered during the addition reaction, as described in DE199 60 148 A1.

The addition reaction of the alkylene oxides is carried out under thecustomary conditions, at temperatures in the range from 60 to 180° C.,preferably from 90 to 140° C., in particular from 100 to 130° C., andpressures in the range from 0 to 20 bar, preferably in the range from 0to 10 bar and in particular in the range from 0 to 5 bar. The mixture ofstarter substance and DMC catalyst can be pretreated by stripping priorto commencement of the alkoxylation, as taught by WO 98/52689.

In a further embodiment, for example as described in DD 203734/735, oneor more further starter alcohols can be metered in during the synthesisin addition to the alkylene oxides. These further starter alcohols maybe identical to or different from those charged initially.

After the addition reaction of the alkylene oxides is complete, thepolyether alcohol is worked up in a customary fashion by removingunreacted alkylene oxides and other volatile constituents, usually bydistillation, steam stripping or gas stripping and/or otherdeodorization methods. If necessary, a filtration can also be carriedout.

The production of the flexible polyurethane foams of the presentinvention can likewise be carried out by customary and known methods.

As regards the starting compounds used for the process of the presentinvention, the following details may be provided:

As polyisocyanates a), it is possible to use all isocyanates having twoor more isocyanate groups in the molecule for the process of the presentinvention. Both aliphatic isocyanates such as hexamethylene diisocyanate(HDI) or isophorone diisocyanate (IPDI) or preferably aromaticisocyanates such as tolylene diisocyanate (TDI), diphenylmethanediisocyanate (MDI) or mixtures of diphenylmethane diisocyanate andpolymethylenepolyphenylene polyisocyanates (crude MDI), preferably TDIand MDI, particularly preferably TDI, can be used. It is also possibleto use isocyanates which have been modified by incorporation ofurethane, uretdione, isocyanurate, allophanate, iretonimine and othergroups, known as modified isocyanates. Preferred prepolymers are MDIprepolymers having an NCO content of from 20 to 35% or mixtures thereofwith polymethylenepolyphenylene polyisocyanates (crude MDI).

The polyether alcohols b) which are used according to the presentinvention and are prepared by addition of alkylene oxides onto compoundsderived from renewable raw materials using DMC catalysts can be usedeither alone or in combination with other compounds having at least twohydrogen atoms which are reactive toward isocyanate groups.

As compounds having at least two active hydrogen atoms b) which can beused together with the polyether alcohols used according to the presentinvention, it is possible to employ, in particular, polyester alcoholsand preferably polyether alcohols having a functionality of from 2 to16, in particular from 2 to 8, preferably from 2 to 4, and a meanmolecular weight M_(W) in the range from 400 to 20000 g/mol, preferablyfrom 1000 to 8000 g/mol.

The polyether alcohols which are, if desired, used together with thepolyether alcohols used according to the present invention can beprepared by known methods, usually by catalytic addition of alkyleneoxides, in particular ethylene oxide and/or propylene oxide, ontoH-functional starter substances or by condensation of tetrahydrofuran.H-Functional starter substances used are, in particular, polyfunctionalalcohols and/or amines. Preference is given to using water, dihydricalcohols, for example ethylene glycol, propylene glycol or butanediols,trivalent alcohols, for example glycerol or trimethylolpropane, orhigher-hydric alcohols such as pentaerythritol, sugar alcohols, forexample sucrose, glucose or sorbitol. Preferred amines are aliphaticamines having up to 10 carbon atoms, for example ethylenediamine,diethylenetriamine, propylenediamine, or amino alcohols such asethanolamine or diethanolamine. As alkylene oxides, preference is givento using ethylene oxide and/or propylene oxide, with an ethylene oxideblock frequently being added on at the end of the chain in the case ofpolyether alcohols which are used for producing flexible polyurethanefoams. Catalysts used in the addition reaction of the alkylene oxidesare, in particular, basic compounds, among which potassium hydroxide hasachieved the greatest industrial importance. When a low content ofunsaturated constituents in the polyether alcohols is desired, DMCcatalysts can also be used as catalysts for preparing these polyetheralcohols.

For particular application areas, in particular for increasing thehardness of the flexible polyurethane foams, it is also possible to makeconcomitant use of polymer-modified polyols. Such polyols can beprepared, for example, by in-situ polymerization of ethylenicallyunsaturated monomers, preferably styrene and/or acetonitrile, inpolyether alcohols. Polymer-modified polyether alcohols also includepolyether alcohols containing polyurea dispersions, which are preferablyprepared by reaction of amines with isocyanates in polyols.

To produce flexible foams and integral foams, use is made of, inparticular, bifunctional and/or trifunctional polyether alcohols. Rigidfoams are produced using, in particular, polyether alcohols which havebeen prepared by addition of alkylene oxides onto tetrafunctional orhigher-functional starters, e.g. sugar alcohols or aromatic amines.

To produce molded flexible foams and highly elastic flexible foams bythe process of the present invention, preference is given to usingbifunctional and/or trifunctional polyether alcohols which bear primaryhydroxyl groups, preferably to an extent of over 50%, in particularpolyether alcohols having an ethylene oxide block at the end of thechain or those based only on ethylene oxide.

To produce flexible slabstock foams by the process of the presentinvention, preference is given to using bifunctional and/ortrifunctional polyether alcohols which bear secondary hydroxyl groups,preferably to an extent of over 90%, in particular polyether alcoholshaving a propylene oxide block or a random propylene oxide and ethyleneoxide block at the end of the chain or those which are based only onpropylene oxide.

The compounds b) having at least two active hydrogen atoms also includechain extenders and crosslinkers. Chain extenders and crosslinkers usedare preferably 2- and 3-functional alcohols having molecular weights offrom 62 to 800 g/mol, in particular in the range from 60 to 200 g/mol.Examples are ethylene glycol, propylene glycol, diethylene glycol,triethylene glycol, dipropylene glycol, tripropylene glycol, lowmolecular weight polypropylene oxide and polyethylene oxides, e.g.Lupranol® 1200, 1,4-butanediol, glycerol or trimethylolpropane. Ascrosslinkers, it is also possible to use diamines, sorbitol, glycerol,alkanolamines. If chain extenders and crosslinkers are used, they arepreferably employed in an amount of up to 5% by weight, based on theweight of the compound having at least two active hydrogen atoms.

The process of the present invention is usually carried out in thepresence of activators, for example tertiary amines or organic metalcompounds, in particular tin compounds. As tin compounds, preference isgiven to using divalent tin salts of fatty acids, e.g. tin dioctoate,and organotin compounds such as dibutyltin dilaurate.

As blowing agent c) for producing the polyurethane foams, preference isgiven to using water which reacts with the isocyanate groups to liberatecarbon dioxide. Water is preferably used in an amount of from 0.5 to 6%by weight, particularly preferably in an amount of from 1.5 to 5.0% byweight. Together with or in place of water, it is also possible to usephysically active blowing agents, for example carbon dioxide,hydrocarbons such as n-pentane, isopentane or cyclopentane, cyclohexane,or halogenated hydrocarbons such as tetrafluoroethane,pentafluoropropane, heptafluoropropane, pentafluorobutane,hexafluorobutane or dichloromonofluoroethane. The amount of physicalblowing agent is preferably in the range from 1 to 15% by weight, inparticular from 1 to 10% by weight, and in this case the amount of wateris preferably in the range from 0.5 to 10% by weight, in particular from1 to 5% by weight. Among the physical blowing agents, preference isgiven to carbon dioxide which is preferably employed in combination withwater.

To produce the flexible polyurethane foams of the present invention,stabilizers and auxiliaries and/or additives can usually also be used.

Suitable stabilizers are, in particular, polyether siloxanes, preferablywater-soluble polyether siloxanes. These compounds generally have astructure in which a long-chain copolymer of ethylene oxide andpropylene oxide is joined to a polydimethylsiloxane radical. Furtherfoam stabilizers are described in U.S. Pat. Nos. 2,834,748, 2,917,480and U.S. Pat. No. 3,629,308.

The reaction may, if desired, be carried out in the presence ofauxiliaries and/or additives such as fillers, cell regulators,surface-active compounds and/or flame retardants. Preferred flameretardants are liquid flame retardants based on halogen-phosphoruscompounds, e.g. trichloropropyl phosphate, trichloroethyl phosphate, andhalogen-free flame retardants such as Exolit® OP 560 (ClariantInternational Ltd).

Further information on the starting materials, catalysts and auxiliariesand additives used may be found, for example, in theKunststoff-Handbuch, Volume 7, Polyurethane, Carl-Hanser-Verlag, Munich,1^(st) edition 1966, 2^(nd) edition 1983 and 3^(rd) edition 1993.

To produce the polyurethanes of the present invention, the organicpolyisocyanates are reacted with the compounds having at least twoactive hydrogen atoms in the presence of the abovementioned blowingagents and, if desired, the catalysts and auxiliaries and/or additives.

In the production of the polyurethanes of the present invention, theisocyanate and the polyol component are usually combined in such anamount that the equivalence ratio of isocyanate groups to the sum of theactive hydrogen atoms is from 0.7 to 1.25, preferably from 0.8 to 1.2.

The polyurethane foams are preferably produced by the one-shot process,for example with the aid of the high-pressure or low-pressure technique.The foams can be produced in open or closed metallic molds or bycontinuous application of the reaction mixture to conveyor belts toproduce slabstock foams.

To produce molded flexible foams, it is particularly advantageous toemploy the two-component method in which a polyol component and anisocyanate component are prepared and foamed. The components arepreferably mixed at from 15 to 90° C., more preferably from 20 to 60° C.and particularly preferably from 20 to 35° C., and introduced into themold or onto the conveyor belt. The temperature in the mold is usuallyin the range from 20 to 110° C., preferably from 30 to 60° C. andparticularly preferably from 35 to 55° C.

Flexible slabstock foams can be foamed in discontinuous or continuousplants, for example by the Planiblock process, the Maxfoam process, theDraka-Petzetakis process and the Vertifoam process.

The flexible polyurethane foams produced by the process of the presentinvention have a significantly reduced odor, significantly reducedvalues for fogging and a significantly reduced crack formation togetherwith an improved compressive set, both before and after aging, comparedto otherwise identical products in which the polyether alcohols usedaccording to the present invention have been prepared from renewable rawmaterials by means of basic catalysts. Furthermore, the foams of thepresent invention have a higher proportion of open cells, which isreflected, for example, in an increased air permeability.

The invention is illustrated by the following examples.

EXAMPLES

Preparation of Polyether Alcohols Using DMC Catalysis

The following properties have been determined by the specifiedstandards, internal test methods or measurement methods: Water contentin % by weight: DIN 51777 Hydroxyl number in mg KOH/g: DIN 53240 Acidnumber in mg KOH/g: DIN EN ISO 3682 Viscosity (25° C.) in mPa · s: DIN51 550 Color number Pt/Co: DIN ISO 6271 Alkalinity in ppm: titrimetricM_(w) in g/mol: mean weight average molecular weight determined by meansof gel permeation Polydispersity D = M_(w)/M_(N) determined by means ofgel permeation Odor: test method PPU 03/03-04 of Feb. 15, 2002Determination of the Odor by Test Method PPU 03/03-04 of Jan. 15, 2001

100 g of the polyetherol to be examined is weighed into a new, dry glassbottle (250 ml) having a screw cap. The determination of the odor iscarried out at 25° C. Before opening the glass bottle, this is brieflyswirled. After the subjective odor test, the glass bottle is once againclosed tightly. The next test may take place only after 15 minutes. Theassessment is carried out by a total of 5 fixed, nominated testers. Theassessment of the odor is carried out according to the following scale:1.0 no odor 1.3 just discernible odor 1.5 discernible pleasant odor 1.7pleasant slightly acrid odor 2.0 slightly unpleasant odor 3.0 unpleasantodor 4.0 smells strongly 5.0 stinks

After the odor assessment of the testers, the odor value is determinedby majority decision and documented. If no majority decision can beestablished, the odor evaluation is repeated at a later point in time.If the ability of a tester to evaluate the odor is restricted by dullingof senses, e.g. a cold, etc., the test is carried out by anothernominated tester.

Example 1

8750 g of castor oil (grade DAB from Alberdingk Boley, hydroxyl number:160 mg KOH/g) were mixed with 50 g of a 5.97% strength suspension of azinc hexacyanocobaltate (corresponding to 150 ppm of DMC catalyst, basedon the product to be prepared) in a 20 liter stirred tank reactor anddewatered at 120° C. and a pressure of about 40 mbar until the watercontent was below 0.02% by weight. 400 g of propylene oxide weresubsequently added and the commencement of the reaction, which could berecognised by a brief increase in temperature and a rapid drop in thereactor pressure, was awaited. At the same temperature, 16450 g of amixture of 9250 g of propylene oxide and 2000 g of ethylene oxide weremetered in over a period of 1.5 hours. After a constant reactor pressurehad been reached, unreated monomers and other volatile constituents weredistilled off under reduced pressure and the product was drained. Thepolyether alcohol was not worked up in an additional deodorizationcolumn.

The colorless polyether alcohol obtained had the following properties:hydroxyl number: 70.8 mg KOH/g acid number: 0.007 mg KOH/g watercontent: 0.017% by weight viscosity (25° C.): 610 mPa · s color number:72 mg of Pt/l M_(w) 2392 g/mol polydispersity D: 1.2208 odor: 1.9

Example 2

The procedure of Example 1 was repeated, but 6300 g of castor oil DABwere reacted with 13840 g of a mixture of 11870 g of PO and 1970 g ofEO. In addition, the polyether alcohol was worked up in a deodorizationcolumn.

The colorless polyether alcohol obtained had the following properties:hydroxyl number: 50.9 mg KOH/g acid number: 0.007 mg KOH/g watercontent: 0.012% viscosity (25° C.): 718 mPa · s color number: 85 mg ofPt/l M_(w) 3053 g/mol polydispersity D 1.1625 odor: 1.5

Example 3

The procedure of Example 1 was repeated, but 11250 g of castor oil DABwere reacted with 8750 g of propylene oxide. In addition, the polyetheralcohol was worked up in a deodorization column.

The colorless polyether alcohol obtained had the following properties:hydroxyl number: 91.0 mg KOH/g acid number: 0.007 mg KOH/g watercontent: 0.010% viscosity (25° C.): 597 mPa · s color number: 96 mg ofPt/l M_(w) 1865 g/mol polydispersity D 1.1872 odor: 1.5

Example 4 (Comparative Example)

16 kg of castor oil DAB were admixed with 60 g of solid potassiumhydroxide in a 50 liter stirred tank reactor and stirred at 110° C. forhalf an hour. After checking the water content, 5.1 kg of propyleneoxide were introduced at such a rate that the reactor pressure did notexceed 7 bar. A mixture of 28.6 kg of propylene oxide and 5.5 kg ofethylene oxide were subsequently introduced, once again at such a ratethat the pressure did not exceed 7 bar. After an after-reaction phase,volatile constituents and unreacted alkylene oxides were distilled offunder reduced pressure and the contents of the reactor were admixed with4% by weight of water. The alkaline reaction mixture was neutralizedwith 80 mol % of the stoichiometric amount, based on the alkalinity, ofphosphoric acid and 0.1% by weight of Ambosol and the salts formed werefiltered off via a deep bed filter.

In addition, the polyether alcohol was worked up in a deodorizationcolumn.

The colorless polyether alcohol obtained had the following properties:hydroxyl number: 51.8 mg KOH/g acid number: 0.738 mg KOH/g watercontent: 0.046% viscosity (25° C.): 593 mPa · s color number Pt/Co: 356Alkalinity: 22 mg of K/kg M_(w) g/mol (data to follow) polydispersity D(data to follow) odor: 1.7

Example 5 (Comparative Example)

The procedure of Example 4 was repeated, but 26.0 kg of castor oil werereacted with 17.0 kg of ethylene oxide and 17.0 kg of propylene oxide.

The polyetherol was not worked up in a deodorization column.

The colorless polyether alcohol obtained had the following properties:hydroxyl number: 82.6 mg KOH/g acid number: 0.840 mg KOH/g watercontent: 0.023% viscosity (25° C.): 535 mPa · s color number Pt/Co: 346Alkalinity: 64 mg of K/kg M_(w) g/mol (data to follow) polydispersity D(data to follow) odor: 3.0Production of Flexible Polyurethane Foams

Examples 6 to 8 (Comparative Examples) and Examples 9 to 10

The starting materials listed in Table 1 were reacted in the ratiosspecified in Table 1.

All components apart from the isocyanate Lupranat® T80A and Desmodur®T65were firstly combined by intensive mixing to form a polyol component.The Lupranat® T80 A and, if applicable, Desmodur® T65 were then addedwhile stirring and the reaction mixture was poured into an open mold inwhich it foamed to produce the polyurethane foam. The properties of thefoams obtained are shown in Table 1.

The following properties were determined by the specified standards,operating procedures and test methods: Foam density in kg/m³ DIN EN ISO845 VOC ricinoleic acid ring in ppm PB VWL 709 FOG ricinoleic acid ringin ppm PB VWL 709 air permeability in dm³/min DIN EN ISO 7231compressive strength, 40% deformation in kPa DIN EN ISO 2439 indentationhardness, 25% deformation DIN EN ISO 2439 indentation hardness, 40%deformation DIN EN ISO 2439 indentation hardness, 65% deformation DIN ENISO 2439 elongation in % DIN EN ISO 1798 tensile strength in kPa DIN ENISO 1798 rebound resilience in % DIN EN ISO 8307 compressive set in %DIN EN ISO 3386 wet compressive set in % operating procedure AAU10-131-041 of Feb. 6, 2002

Determination of the wet compressive set in accordance with theoperating procedure AA U10-131-041 of Feb. 6, 2002:

The height of the foam test specimens having dimensions of 50 mm×50mm×25 mm was determined at a previously marked point by means of asliding caliper or caliper gauge. The test specimens are subsequentlyplaced between two pressure plates and compressed to a height of 7.5 mmwith the aid of spacers using a cladding apparatus.

Storage at 50° C. and 95% relative atmospheric humidity in a controlledatmosphere cabinet commences immediately after clamping. After 22 hours,the foam test specimens are quickly removed from the clamping apparatusand placed on a surface having low thermal conduction (tray) for 30minutes in the standard atmosphere to allow relaxation. The height atthe marked point is subsequently redetermined using the same measurementmethod.

The wet compressive set is expressed as a ratio of the deformation andis calculated as follows:Wet compressive set=h ₀ −h _(R)*100/(h ₀−7.5 mm) in %h₀ original height in mm

h_(R) height of the test specimen after the test, in mm TABLE 1 Ex. 6Ex. 7 Ex. 8 OHN (C) (C) (C) Ex. 9 Ex. 10 Lupranol ® 2080 50.00Polyether, prepared as 82.6 100.00 described in Example 5 Polyether,prepared as 51.8 100.00 100.00 described in Example 4 Polyether,prepared as 91.0 50.00 described in Example 3 Polyether, prepared as70.8 100.00 described in Example 1 Tegoamin ® B4900 0 1.40 0.80 0.801.20 1.20 Niax ® A1 560 0.05 0.05 0.05 0.05 0.05 Dabco ® 33LV 425.8 0.150.15 0.15 0.20 0.20 Kosmos ® 29 0 0.23 0.20 0.23 0.23 0.30 Water(added.) 6233 3.70 2.00 2.00 3.80 3.80 Lupranat ® T80A index 110 112 112Lupranat ® T80A : Desmodur ® T65 113 113 1:1 index Comment rupturedCream time in s 13 8 9 12 17 Fiber time in s 75 105 100 90 90 Rise timein s 85 120 120 95 100 Air permeability in dm³/min 69 48 132 144 VOCricinoleic acid ring in ppm 82 105 0 0 FOG ricinoleic acid ring in ppm3239 354 0 0 Foam density in kg/m³ 25.3 43.7 25.9 25.5 Tensile strengthin kPa 71 55 80 82 Elongation in % 76 139 80 90 Compressive strength,40% 4.7 2.7 4.5 4.1 deformation, in kPa Compressive set in % 8.8 6.5 3.13.0 Wet compressive set 25.3 23.2 6.9 7.0 Rebound resilience in % 26 4545 42 Indentation hardness, 25% 172 73 144 116 deformation Indentationhardness, 40% 249 108 180 147 deformation Indentation hardness, 65% 513248 353 292 deformation Aging under hot and humid conditions inaccordance with DIN EN ISO 2240 Compressive strength, 40% 2.5 1.6 3.13.0 deformation, in kPa Tensile strength in kPa 65 35 88 90 Elongationin % 70 130 140 143 Compressive set in % 18.3 12.4 3.0 3.1Notes on the table:Lupranol ® 2080: polyetherol having a hydroxyl number of 48 mg KOH/g anda viscosity of 540 mPa · s (BASF Aktiengesellschaft)Dabco ® 33 LV: 1,4-diazabicyclo[2.2.2]-octane (33%) in dipropyleneglycol (67%) (Air Products and Chemicals, Inc.)Niax ® A1: bis(2-dimethylaminoethyl) ether (70%) in dipropylene glycol.(30%) (Crompton Corporation)Kosmos ® 29: tin(II) salt of ethylhexanoic acid (Degussa AG)Tegostab ® B 4900: silicone stabilizer (Degussa AG)Lupranat ® T80: tolylene 2,4-/2,6-diisocyanate mixture in a ratio of80:20 (BASF Aktiengesellschaft)Desmodur ® T65: tolylene 2,4-/2,6-diisocyanate mixture in a ratio of65:35 (BAYER AG)

1. A process for producing a low-emission flexible polyurethane foam byreacting a) a polyisocyanate with b) a compound having at least twohydrogen atoms which are reactive toward an isocyanate group, whereinsaid compound is a polyether alcohol which has been prepared by additionof an alkylene oxide to a compound derived from renewable raw materialsselected from the group consisting of castor oil, polyhydroxy fattyacids, ricinoleic acid, hydroxyl-modified oils, grapeseed oil, blackcaraway oil, pumpkin seed oil, borage seed oil, soybean oil, wheat germoil, rapeseed oil, sunflower oil, peanut oil, apricot kernel oil,pistachio nut oil, almond oil, olive oil, macadamia nut oil, avocadooil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, eveningprimrose oil, wild rose oil, hemp oil, safflower oil, walnut oil, andhydroxyl-modified fatty acids and fatty acid esters based on myristoleicacid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid,gadoleic acid, erucic acid, nervonic acid, linoleic acid, α- andγ-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid,clupanodonic acid and cervonic acid using a DMC catalyst.
 2. A processas claimed in claim 1, wherein said polyether alcohol has a meanmolecular weight M_(w) in the range from 400 to 20 000 g/mol.
 3. Aprocess as claimed in claim 1, wherein said polyether alcohol has a meanmolecular weight in the range from 1000 to 8000 g/mol.
 4. A process asclaimed in claim 1, wherein said polyether alcohol has a content ofcyclic fatty acid esters of not more than 50 ppm.
 5. A process asclaimed in claim 1, wherein said polyether alcohol has a content ofcyclic fatty acid esters of not more than 10 ppm.
 6. A process asclaimed in claim 1, wherein said low-emission flexible polyurethane foamhas a compressive set of not more than 7%.
 7. A process as claimed inclaim 1, wherein said low-emission flexible polyurethane foam has acompressive set, after aging in accordance with DIN EN ISO 2440, of notmore than 10%.
 8. A low-emission flexible polyurethane slabstock foamproduced by the process as claimed in claim
 1. 9. A motor vehiclecomprising said low-emission flexible polyurethane slabstock foam asclaimed in claim
 8. 10. A furniture or a mattress comprising saidlow-emission flexible polyurethane slabstock foam as claimed in claim 8.11-12. (canceled)
 13. The low-emission flexible polyurethane slabstockfoam as claimed in claim 8 having reduced crack formation.
 14. Thelow-emission flexible polyurethane slabstock foam as claimed in claim 8having a reduced odor and a reduced fogging value.